The invention relates to manuals for use in electronic organs and analogous musical instruments. More particularly, the invention relates to improvements in manuals with piano effect wherein each key is pivotable from idle position about a normally horizontal axis against the resistance of a spring and carries a pusher which can pivot a reaction member so that the latter is caused to turn about a second normally horizontal axis. Still more particularly, the invention relates to improvements in manuals wherein the initial stage of depression of the key from its idle position encounters a greater resistance and the resistance thereupon decreases as the pusher of the key and the reaction member are caused to move relative to each other. As a rule, the greater resistance is offered by the mass and inertia of a weight which is carried by the reaction member, and the resistance decreases as a result of increasing distance of the locus of contact between the pusher and the reaction member from the pivot axis of the reaction member.
As used herein, the term "electronic organs" is intended to embrace so-called keyboards as well as electronic pianos.
Published European patent application No. 0 270 966 of Franz discloses a manual which can be used in an electronic organ and wherein the touch of the keys is intended to resemble that of the keys in a standard piano. This is proposed to be accomplished in that, during the initial stage of depression of a key, the full force or substantially the entire force which is applied to the depressible end portion of the key is transmitted to the reaction member by a pusher on the key, namely to a first arm of the reaction member which carries the weight, i.e., in the same way as in the action of a standard manual for use in mechanical pianos. The ratio of distance of the point of contact between the pusher and the reaction member from the pivot axis of the reaction member to the distance of the center of gravity of the weight-carrying first arm of the reaction member from the pivot axis of the reaction member is very small. This, combined with the aforementioned transmission of full force to the reaction member, entails a pronounced initial acceleration of the reaction member and results in the development of a large reaction force (product of mass and acceleration), just as in a standard piano. A second arm of the reaction member causes the pusher to pivot shortly after the start of depression of the key so that the direction of application of the force from the pusher to the reaction member is changed from a direction substantially at right angles to the motion receiving portion of the first arm of the reaction member (namely at right angles to a tangent to the convex pusher-contacting surface of the first arm) to a direction such that the pusher slides along the adjacent surface of the first arm. Therefore, only a certain component of the force which was previously transmitted by the pusher continues to be transmitted to the adjacent surface of the first arm of the reaction member. At the same time, the pusher moves away from the pivot axis of the reaction member and, therefore, the reaction force of the reaction member decreases very rapidly to simulate the effect which is customary in standard pianos and is familiar to a person normally or often playing a standard piano.
An advantage of the manual which is disclosed by Franz is that each action of the manual can employ a simple rod- or stud-shaped straight pusher without an additional lever arm which is necessary in connection with pusher tongues of standard piano actions and without the need for release elements which must be employed in standard actions. The second arm of the reaction member in the action of Franz carries out the function of the release element. A composite joint between the pusher and the key enables the second arm of the reaction member to change the orientation of the pusher relative to the adjacent surface of the reaction member upon completion of the first stage of pivoting of the key from its idle position. This second arm of the reaction member is provided with a cushion serving to reduce the noise which is likely to be generated during return movement of the pusher to its normal or initial position. A drawback of the cushion is that its initial cost and its mounting contribute to the overall cost of the action. Moreover, if the cushion is not readily deformable, its noise-suppressing action is likely to be unsatisfactory. On the other hand, a readily deformable cushion prevents predictable and reproducible selection of that stage of pivoting of the key from its idle position at which the resistance to further depression of the key decreases. The reason is that it is difficult to invariably ensure that the pusher will begin to slide with reference to the first arm of the reaction member in response to a predetermined angular displacement of the key from its idle position. Still further, a relatively thick and soft cushion is likely to alter (lose) its deformability with time so that the noise-suppressing action of such cushion becomes unsatisfactory after a relatively short period of use of the action.
U.S. Pat. No. 4,217,803 to Dodds discloses an action wherein the pusher is rigid with the key. Similar actions are disclosed in German Auslegeschrift No. 24 26 016 of Aliprandi and in German Pat. No. 36 01 892 to Franz. East German patent No. 252 696/ discloses a rigid pusher.